Homopolymers or copolymers of .alpha.-olefin are widely used because they are inexpensive and have excellent mechanical strength, luster, transparency, molding properties, wrapping properties, and resistance to chemicals. These .alpha.-olefin polymers, however, have a poor affinity for other substances due to their non-polar molecular structures and therefore are seriously inferior in properties such as adhesive properties, coating properties, printability and antistatic properties.
In order to overcome the above problems, various techniques have been proposed, including a method of partially oxidizing the polymers by treating with a mixed solution containing chromic acid or by flame treatment; a method of grafting a polar group-containing compound such as maleic anhydride, methyl methacrylate, or acrylonitrile, onto the polymers by the action of a radical initiator; and a method of copolymerizing the monomers with polar group-containing comonomers.
These conventional methods, however, have various disadvantages.
The above first method has disadvantages in that the mixed solution is strongly acidic and poisonous, it is difficult to carry out the flame treatment satisfactorily, the oxidation effect is not uniform, and only the surface of a molding can be treated. Therefore, the first method is greatly limited in its industrial use.
The second method has been put to practical use and conducted on a commercial scale in some factories. In this method, however, the polymers to be modified are degraded or undergo cross-linking, thereby leading to a reduction in physical properties thereof. Thus the second method fails to produce polymers satisfying the increasingly severer requirements concerning conditions and manner of use.
The third method has many problems to be solved in its practical use and could not be conducted on a commercial scale.